Pioneer round of translation occurs during serum starvation

The pioneer round of translation plays a role in translation initiation of newly spliced and exon junction complex (EJC)-bound mRNAs. Nuclear cap-binding protein complex CBP80/20 binds to those mRNAs at the 5'-end, recruiting translation initiation complex. As a consequence of the pioneer round of translation, the bound EJCs are dissociated from mRNAs and CBP80/20 is replaced by the cytoplasmic cap-binding protein eIF4E. Steady-state translation directed by eIF4E allows for an immediate and rapid response to changes in physiological conditions. Here, we show that nonsense-mediated mRNA decay (NMD), which restricts only to the pioneer round of translation but not to steady-state translation, efficiently occurs even during serum starvation, in which steady-state translation is drastically abolished. Accordingly, CBP80 remains in the nucleus and processing bodies are unaffected in their abundance and number in serum-starved conditions. These results suggest that mRNAs enter the pioneer round of translation during serum starvation and are targeted for NMD if they contain premature termination codons.     

Atomic force microscopy study of the antigen‐antibody binding force on patient cancer cells based on ROR1 fluorescence recognition

Knowledge of drug–target interaction is critical to our understanding of drug action and can help design better drugs. Due to the lack of adequate single‐molecule techniques, the information of individual interactions between ligand‐receptors is scarce until the advent of atomic force microscopy (AFM) that can be used to directly measure the individual ligand‐receptor forces under near‐physiological conditions by linking ligands onto the surface of the AFM tip and then obtaining force curves on cells. Most of the current AFM single‐molecule force spectroscopy experiments were performed on cells grown in vitro (cell lines) that are quite different from the human cells in vivo. From the view of clinical practice, investigating the drug–target interactions directly on the patient cancer cells will bring more valuable knowledge that may potentially serve as an important parameter in personalized treatment. Here, we demonstrate the capability of AFM to measure the binding force between target (CD20) and drug (rituximab, an anti‐CD20 monoclonal antibody targeted drug) directly on lymphoma patient cancer cells under the assistance of ROR1 fluorescence recognition. ROR1 is a receptor expressed on some B‐cell lymphomas but not on normal cells. First, B‐cell lymphoma Raji cells (a cell line) were used for ROR1 fluorescence labeling and subsequent measurement of CD20‐rituximab binding force. The results showed that Raji cells expressed ROR1, and the labeling of ROR1 did not influence the measurement of CD20‐rituximab binding force. Then the established experimental procedures were performed on the pathological samples prepared from the bone marrow of a follicular lymphoma patient. Cancer cells were recognized by ROR1 fluorescence. Under the guidance of fluorescence, with the use of a rituximab‐conjugated tip, the cellular topography was visualized by using AFM imaging and the CD20‐Rituximab binding force was measured by single‐molecule force spectroscopy. Copyright © 2013 John Wiley & Sons, Ltd.     

The Janzen-Connell effect on the population dynamics of a Fagus engleriana- Cyclobalanopsis oxyodon community in a subtropical zone of China

The Janzen-Connell (J-C) hypothesis provides a mechanism explaining the high species diversity in tropical rainforests. It postulates that predation could cause greater mortality on seeds and seedlings near their parental trees. In this study, we tested the hypothesis in a subtropical zone, a mixed evergreen-deciduous broad-leaved forest dominated by the Fagus engleriana and Cyclobalanopsis oxyodon. The study area was in the Shennongjia region, a key area of biodiversity conserva-tion in both China and the world. The recruitment probability index was used to detect the J-C effect on nine species of the community, which were more than 50 individuals. Six large adults of each species were selected, and the numbers of saplings and adults were counted at the distance intervals of 0-5, 5-10, 10-15, 15-20, and 20-25 m from each focal tree. Two species in saplings stage and six in adult stage supported the J-C hypothesis, but their χ2 was not significant. Three species, the F. engleri-ana, Rhododendron hypoglaucum, and Toona sinensis, showed a strong Hubbell pattern in the adult stage. Because of these results, we reject the J-C hypothesis and conclude that species could recruit near the conspecific trees in subtropical forest. The reasons why the J-C hypothesis fails to explain the species diversity in this community are the shortage of seed-consuming agents of subtropical forest and the influence of microsite topo-graphic variation.     

IL-13抑制剂在损伤大鼠尾椎间盘退变中的作用研究

为了探讨IL-13细胞因子在损伤后大鼠椎间盘退变中的影响,建立了大鼠尾椎间盘退变模型,给予IL-13抑制剂sIL-13Rα2-Fc进行干预,将实验分为空白、对照、低剂量、中剂量、高剂量干预组。分别于4周及6周后通过HE染色和Masson染色观察椎间盘形态变化并评分;DMMB法定量分析椎间盘中的糖胺多糖(glycosaminoglycan,GAG)、硫酸软骨素(chondroitin sulfate,CS)、硫酸角质素(keratan sulfate,KS)、透明质酸(hyaluronic acid,HA)含量变化;RT-PCR分析Ⅰ型和Ⅱ型胶原蛋白的mRNA表达水平;蛋白质印迹分析Ⅰ型和Ⅱ型胶原蛋白含量。HE和Masson染色显示与对照组相比,干预组椎间盘病理改变减小,纤维环排列更规则,破裂部位减小,NP细胞数量增加,胶原纤维减少。sIL-13Rα2-Fc干预增加了糖胺多糖、透明质酸含量,增加了硫酸软骨素/硫酸角质素比,减少了Ⅰ型胶原蛋白的表达,并增加了Ⅱ型胶原蛋白。结果表明IL-13抑制剂sIL-13Rα2-Fc可有效减轻椎间盘退变,并且与作用时间和浓度成正相关。     

Self-organized pullulan/deoxycholic acid nanogels: Physicochemical characterization and anti-cancer drug-releasing behavior

The objective of this study was to develop new self-organized nanogels as a means of drug delivery in patients with cancer. Pullulan (PUL) and deoxycholic acid (DOCA) were conjugated through an ester linkage between the hydroxyl group in PUL and the carboxyl group in DOCA. Three types of PUL/DOCA conjugates were obtained, differing in the number of DOCA substitutions (DS; 5, 8, or 11) per 100 PUL anhydroglucose units. The physicochemical properties of the resulting nanogels were characterized by dynamic light scattering, transmission electron microscopy, and fluorescence spectroscopy. The mean diameter of DS 11 was the smallest (approx. 100 nm), and the size distribution was unimodal. To determine the organizing behavior of these conjugates, we calculated their critical aggregation concentrations (CACs) in a 0.01-M phosphate buffered saline solution. They were 10.5×10⁻⁴ mg/mL, 7.2×10⁻⁴ mg/mL, and 5.6×10⁻⁴ mg/mL for DS 5, 8, and 11, respectively. This indicates that DOCA can serve as a hydrophobic moiety to create self-organized nanogels. To monitor the drug-releasing behavior of these nanogels, we loaded doxorubicin (DOX) onto the conjugates. The DOX-loading efficiency increased with the degree of DOCA substitution. The release rates of DOX from PUL/DOCA nanogels varied inversely with the DS. We concluded that the PUL/DOCA nanogel has some potential for use as an anticancer drug carrier because of its low CAC and satisfactory drug-loading capacity.